1. Field of the Invention
The present invention relates to an antitheft system of vehicles propelled by an internal combustion engine such as motorcycles and, more specifically, to an electronic key system (in other words, a vehicle antitheft system) in which verification of ID codes is made between a transmitter-receiver that a user carries and a control device mounted on a vehicle, whereby the internal combustion engine is allowed to start only in the case of being the start request from an allowable user.
2. Description of the Related Art
For example, in one of the conventional vehicle antitheft systems, verification of respective stored ID codes is made between a transmitter-receiver (mobile unit) that a driver carries and a transmitter-receiver on the vehicle side; and as a result of verification, in case of coincidence of both ID codes, an engine of the vehicle is allowed to start.
Furthermore, in the case of two-wheel vehicles as compared with four-wheel vehicles, there is a high possibility that a mobile unit is missed during traveling due to any accident. In the case where the mobile unit is missed, it is necessary to notify a driver of being missed.
As a system of warning when a driver drops a mobile unit, there is a vehicle electronic key system as disclosed in, for example, the Japanese Patent Publication (unexamined) No. 114860/2004.
This Japanese Patent Publication (unexamined) No. 114860/2004 discloses “a vehicle electronic key system having a control device mounted on an actual vehicle and a mobile transmitter-receiver transmitting a response signal based on receiving a request signal from this control device, the control device including first means for outputting the request signal with respect to a mobile transmitter-receiver based on ON operation of a start switch of the actual vehicle, second means for detecting a response signal from the mobile transmitter-receiver based on the request signal, and third means for making a warning output in the case where no response signal is detected at the second means irrespective of output of the request signal from the first means”.
Further, according to this vehicle electronic key system, it is described that “first, in the case where a user makes a start switch ON without noticing that he carries no mobile transmitter-receiver, or has dropped it, since no response signal is detected at the second means irrespective of output of the request signal from the first means, an alert warning will be outputted through the third means, and thus the user will notice that he carries no mobile transmitter-receiver.
In this manner, the Japanese Patent Publication (unexamined) No. 114860/2004 discloses an electronic key system in which in the case where a user drops a mobile unit during the vehicle being stopped as well as during traveling, this fact can be outputted as an alert warning, thus enabling to make it less frequent to the utmost for a user to miss a mobile unit.
In the above-mentioned vehicle antitheft system (vehicle electronic key system), there may be advantages of vehicle antitheft of four-wheel vehicles driven in a room (driver's cab) of the vehicles that is separated from outside.
However, in the case of two-wheel special vehicles (“two-wheel vehicles” are referred to as auto-bikes, and “special vehicles” are referred to as outboard marine engines, buggy cars, snowmobiles, water-bikes and the like) in which a driver is directly provided with sounds of vehicles themselves (engine sounds), whistles during traveling, extraneous sounds or the like, since they are not vehicles driven in a room separated from outside as are four-wheel vehicles, there are some cases where a driver does not notice that a key is dropped even when his vehicle begins to move.
In addition, even if notification is made with, e.g., lamps, there is the possibility that such warning is missed to notice due to reflection from a meter panel under sunlight.
A further problem exits in that when a driver once stops an engine, moves away without noticing loss of an electronic key, and then returns to his vehicle again and tries to restart the engine, he notices the loss of an electronic key for the first time, and thus cannot make the engine ON.